Chorus control for electric organs



May 24, 19.66 c. R. woLFANGl-:R v3,253,078

CHORUS CONTROL FOR ELECTRIC ORGANS Filed June 19, 1965 4 Sheets-Sheet 1INVENTOR. .C'ur Z Wa/fange/ BY j( i May241956` c R. WOLFANGER CHORUSCONTROL FOR ELECTRIC ORGANS 4 Sheets-Sheet 2 Filed June 19, 1963 N .NE

Ma'y 24, 1966 Filed June 19, 1963 v C. R. WOLFANGER CHORUS CONTROL FORELECTRIC ORGANS 4 Sheets-Sheet 5 May 24, 1966 CHORUS CONTROL FORELECTRIC ORGANS Filed June 19, 1963 C. R. WOLFANGER 4 Sheets-Sheet 4United States Patent() 3,253,078 CHGRUS CONTROL FR ELECTRIC ORGANS CurtR. Wolfanger, Elkhart, Ind., assigner to C. G. Conn, Ltd., Elkhart,Ind., a corporation of Indiana Filed June 19, 1963, Ser. No. 288,965 14Claims. (Cl. 84-1.24)

This invention relates generally to musical instruments and moreparticularly to methods and apparatus for creating a chorus effect inthe tones generated by electronic, electric, and related types of organshaving independent tone sources.

Many organs and similar musical instruments are provided with individualtone sources, such as tone generators or oscillators, which areselectively tuned to different frequencies corresponding to a series ofmusical notes over several octaves of a musical scale. Although eachtone source may be precisely tuned to a selected frequency of the scale,this results in an overly pure, lifeless sound that is objectionable tomany listeners. To add warmth, it is desirable to create a chorus elfectby introducing mild beats when certain notes and chords are played attwo or more pitches, as, for example, by detuning the tone generators sothat some notes will be slightly sharp, others slightly flat, with stillothers remaining unchanged. Although this chorus eifectcan be-created toa limited degree by reducing the stability of the tone sources andallowing the frequency to drift in a somewhat random manner, or byattempting to detune individual ones of the tone sources in a randomfashion, the results are Iless than satisfactory. In the particularinstance of organs utilizing electronic oscillators or generators astone sources, considerations of circuit complexity, space and economicsmake it desirable to use a single or double bank of tone generators sothat the notes for a number of stops are obtained from the same numberof tone generators. Accordingly, there is a limited number of randombeats which may occur, and without a large number of tone generators therandomly occurring beats produced by such techniques will not obtainfull richness on certain notes and chords, may be missing on others, andeven objectionable on still others.

It is therefore among the objects of the present invention to providesimple and economical means for creating -a full chorus effect in organsand related musical instruments having a limited number of tone sources.

Another object is to provide a method of producing beats by octavedetuning according to a predetermined schedule to create a desirablechorus effect in lmusical instruments such as organs and the like.

A further object is to provide, in an electronic organ utilizing alimited number of independent tone generators, simple and practicalmeans for providing a full chorus effect.

Still another object is to provide, in an electronic organ having alimited number of independent tone generators, economical andconveniently operable circuit means to produce a full richness in tonewhen notes and chords are played at two or more pitches.

A feature of the present invention is the provision, in an electricorgan utilizing a limited number of individual tone sources, ofapparatus for shifting the frequency of the tone sources of each octaveby a predetermined amount relative to a standard pitch to result in adesirable chorus effect.

Another feature is the provision of the method of creating a full choruseffect in an organ utilizing a limitednumber of independent tone sourcesby shifting the tuning of the tone sources of each octave a differingdegree in in relation to the tuning of other octaves according to apredetermined tuning pattern.

A further feature is the provision of an electric organ 3,253,078`Patented May 24, 1966 having individual electronic tone generators foreach note of a musical scale, and of a switching arrangement forchanging a circuit parameter determinative of the tuning of the tonegenerators in each octave in a predescribed manner, thereby producingoctave detuning to create a full chorus effect.

Still another feature is the provision, in an electronic organ having asingle bank of independent tone generators, of a simple and convenientlyoperable circuit including a switching arrangement which functions tochange a biasing voltage supplied to individual tone generators so thatselected octaves may be detuned either sharp or flat by a predeterminedamount, which amount differs for each octave of the musical scale.

Further objects, features and attending advantages of the invention willbecome apparent from the following description when taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating the manner in which theinvention is incorporated in an electronic organ;

FIGS. 2-5 and 7 are representative :octave detuning patterns useful inunderstanding the manner in which 'the invention creates a desirablefull chorus effect; and 4 FIG. 6 is a schematic diagram illustrating anadditional way in which the invention may `be incorporated in anelectronic organ.

In practicing the invention there is provided an organ having aplurality of individual tone sources to produce the notes of a musicalscale. The number of tone sources is limited such that although thetones for a given stop on the organ are derived from separate sources,each stop derives tones from the same set of sources. Although the tonesources may include electrical, electronic, electromechanical andmechanical tone generators, in the preferred instance of electronicorgans each tone generator includes an electronic oscillator havingoscillation sustaining means such as a vacuum tube or transistor coupledwith a frequency determining circuit such as a tuned parallel resonantcircuit. The frequency of each tone generator is changeable withinlimits by varying an electrical parameter of the oscillator circuit,such as, for example, by changing a biasing voltage of the vacuum tubeor transistor to result in a shift in impedance of the resonant circuit.

The tone generators are arranged so that selected groupings are providedwith a common variable parameter for determining their frequency suchthat each grouping produces an octave of notes of the musical scale. Inthis manner, several groupings provide a range of octaves, with the tonegenerators of each octave evenly tuned to a standard pitch of themusical scale. To create a full chorus eifect means are provided tochange the electrical parameter provided for each octave of tonegenerators a selected amount, thereby detuning each octave relative toevery other octave according to a predetermined schedule. Thus, someoctaves are tuned sharp and others are tuned flat, each by differingamounts, with all notes of an octave either being detuned by the sameamount or being detuned in fixed increments relative to a standardpitch.

In the accompanying drawings the invention is set forth withparticularity for an electronic organ utilizing vacuum tube triodeoscillators as tone generators, and with the tone generators of eachoctave receiving a biasing voltage from a voltage divider according to apredetermined arrangement. An example of one such organ is the model63() produced by C. G. Conn, Ltd., Elkhart, Indiana, and in circuitdetail forms no part of the invention. It is to be understood that othertypes of tone generators may be used, such as those employingtransistors, and that other electrical parameters may be varied toprovide the octave detuning which creates the full chorus effect,

such as providing voltage or current sensitive impedance elements in thetuned circuit of the oscillator circuit of the tone generators, byvarying the core of a tuning inductor or by adding and removing circuitcomponents to the oscillator tuned circuit by a switching arrangement.And although set forth in terms of detuning entire octaves, each octavemay be broken down into smaller increments as, for example, providingone-half octave detuning.

The system shown schematically in FIG. 1 illustrates circuit means forsupplying bias voltage to several octaves of tone generators of anelectric organ. Vacuum tube oscillator circuits represent two of severaltone generators which may be included in an octave, each of which are ofidentical circuit configuration. Triode 12 has its grid electrodecoupled through capacitor 13 to tuned parallel resonant circuit 14.Tuned circuit 14 includes tuning inductor 15 connected in parallel withcapacitor 16. Tuning inductor 15 of the resonant circuit is centertapped and the tap point is connected to the catl1- ode of triode 12 tothereby provide a Hartly oscillator circuit. Inductor 15 is tunable sothat the tone generator may be tuned to a predetermined frequency for agiven D.C. bias on the grid electrode of triode 12. The grid electrodeof triode 12 is further connected by resistor 18 to octave bias bus 25.Resistor 18 is high valued to provide circuit isolation and the voltagethereby supplied to the grid of triode 12, in conjunction with thesetting of coil 15, establishes the frequency at which the tonegenerator oscillates. To detune the tone generator sharp or ilat from agiven pitch a change in bias voltage supplied to the grid electrode oftriode 12 produces a phase shift in the signal coupled to tuned circuit14 by capacitor 13.

A sine wave, or ute tone, is derived from the cathode of triode 12. Apulse tone is developed across resistor 17,` connected between one side`of tuned circuit 14 and ground reference potential. The pulse tone ishigh in harmonic content to produce string-like sounds. Both the ute andpulse outputs of the tone generator are coupled by key switches forprocessing in the organ in a known manner. In a practical construction,two triodes may be enclosed ina single vacuum envelope to provide twooscillators, as shown. It is to be understood that a number ofadditional oscillators may be provided for coupling to octave bias bus25 by an isolating resistor 18 to provide tone generators for the notesC5B5, making up octave 5 of the organ. In a similar manner, furthergroups of oscillators may be provided with the grid electrode of thetriode 12 connected by resistor 18 to bias busses 22 to 27 to provideoctaves 2-7 in a completed organ'.

Bias voltage for each octave bias bus is obtained from bias network 24.This network includes a voltage dividing network comprised of resistors30 through 37, connected in a series string. Octave bias busses 22-27are connected to the junction points of selective ones of re sistors30-37 to thereby distribute the desired bias voltage to the tonegenerators of each octave. One end of resistor 30, which constitutes oneend of the series voltage dividing string, is connected to the movablecontact 41 of pole 40a of double pole, double throw bias control switch40. Fixed contact 43 of switch pole 40a is connected to ground referencepotential. One end of resistor 37, which constitutes the other end ofthe series string of voltage dividing resistors, is connected to groundreference potential. The movable contact 42 of pole 40b of choruscontrol switch 40 is connected tothe junction point between resistors 34and 35 of the voltage dividing string. This is also the point to whichoctave bias bus 25 is connected to provide bias for th'e tone generatorsof octave 5.

Direct current potential for the bias network 24 is supplied at terminal50. This terminal is also connected by resistor 52 to the xed Contact 44of pole 40b of chorus control switch 40. A second xed contact 45 of pole40a of chorus control switch 40 is connected by resistor 54 to terminal50. The common point between resistor 54 and fixed terminal 45 of choruscontrol switch 40 is connected throughl the secondary winding oftransformer 61 of tremolo generator 60 to the junction point betweenresistors 33 and 34 of bias network 24. Terminal 45 is further bypassedto ground `reference potential by capacitor 56.

Tremolo generator 61) includes triodes 62 and 63 cross coupled bycapacitors 64 and 65 and resistors 66 and 67 to provide a push-pulloscillator circuit. The primary winding of transformer 61 is connectedbetween the anode electrodes of triodes 62 and 63, and shunted bycapacitor 68 to provide a tuned circuit that develops an oscillatingsignal in the frequency range from approximately 5.7 to 7.2 cycles persecond. This signal, when coupled to the secondary winding oftransformer 61, provides an A.C. modulation superimposed upon the octavebias voltages developed by bias network 24. When supplied to the gridelectrodes of individual tone generators, this A.C. modulation causestheir frequency to vary around an established center value to produce atremolo effect. The magnitude of this tremolo voltage may be controlledby switches 70a-70b which are operable to shunt portions of cathoderesistor 72 for triodes 62 and 63 to ground reference potential. Whenboth are closed, as shown, oscillations cease, while successivelyopening switches 70er-7012 provides a higher valued cathode resistancethat results in an increased amplitude of tremolo oscillations.

Chorus control switch 40 is shown in its NORMAL position, that is, in aposition in which the chorus elfect is not created in the organ. In thisposition a D.C. Voltage path is supplied through resistor 52 and pole40b of switch 40 to the junction point between resistors 34 and 35, andhence through resistors 35, 36 and 37 to ground' reference potential. Asecond D.C. Voltage path is supplied through resistor 54 and thesecondary winding of transformer 61 to the junction point betweenresistors 33 and 34, and hence through resistors 33, 32, 31, 30 and apole 40a of switch 40 to ground reference potential. The voltagesdeveloped across the voltage dividing resistors 30-37 in bias network24, when supplied with a D.C. potential in this manner, provides a biasvoltage on each of octave bias busses 20-25 which tunes the tonegenerators for each octave of the organ on pitch. It is to be noted thatwith switch 40 in its NORMAL position the organ may be tuned by standardtechniques. Chorus control switch 40 may be conveniently located on astop tablet of the organ to allow the organist to use the chorus etectat his option or to play the organ as tuned in the standard manner.

When chorus control switch 40 is moved to its CHORUS position, pole 40bis opened and voltage isiremove-d from the junction point betweenresistors 34 and 35. Concurrently pole 40a is opened so that resistor 30is disconnected from ground reference potential and connected instead toxed Contact 45. The D.C. potential at terminal 50 is supplied throughresistor S4 and hence through the series string of resistors 30-37 toground reference potential. The connection through secondary winding 61to the junction point between resistors 33 and 34 remains unchanged.Thus, with switches 40 in CHORUS position the voltages on octave biasbusses 22-24 increase, tuning octaves 2 and 3 sharp, while the voltageon octave bias busses 26 and 27 decreases, tuning octaves 5-7 flat.Octave 4 remains substantially unchanged. In addition, the higheroctaves are tuned llat and progressively smaller increments while thelower octaves are turned sharp and progressively large increments.

In a practically constructed circuit patterned after the system of FIG.1, the following component values were utilized:

Resistors 30, 31, 33, 37 ohms When used in conjunction with 12AU7 dualtriodes connected as tone generators in the manner shown in FIG. 1, andwith a 75 v. D C. potential supplied to terminal 50, the followingchanges in biasing voltages appearing on octave bias busses 22-27 wereobtained:

Octave SW. 40 NORMAL SW. 40 CHORUS (v. .0.) (v. D.

It can be readily seen that the bias voltage for octave 4 increases onlya slight amount, and there is no appreciable detuning of that octave. Onthe other hand, the bias voltage for octaves 2 and 3 increases in longerincrements so that those octaves are detuned progressively sharp, whilethe bias voltage for octaves 5, 6 and 7 decreases in smaller incrementsso that those octaves are detuned progressively flat.

FIG. 2 is a graph showing relative octave tuning patterns which may beobtained with a chorus control system of the above described type. Thehorizontal axis of the curves A and B is divided into octaves 2-7 suchthat octave 2 includes the tone generators for notes C2-B2, octave 3 fornotes C3-B3, octave 4 notes C4-B4, octave 5 notes CS-BS, octave 6 notesC6-B6 and octave 7 notes C7-B7. The vertical axis represents deviationfrom standard tuning in cents. Standard tuning octave 4 contains A440cps. at standard pitch. Curve A represents the tuning pattern withchorus control switch 40 in NOR- MAL position, and curve B representsthe increments of detuning achieved when chorus control switch 40 is inCHORUS position.

The detuning of each octave in curve B is shown to be horizontal torepresent average detuning for each octave for the purposes ofillustration. However, since in a practical application the tonegenerators within an octave are operating at a different frequency whilea fixed bias change is applied thereto. Thus, actual detuning curveswill be somewhat slanted such that the lower notes in an octave are moresharp and the higher notes in an octave are more fiat than the averageshown. This tapering effect further prevents abrupt changes when movingfrom one octave to the next for a more natural effect. It is to be notedthat octave 4 will remain substantially on pitch while lower octaves 2and 3 are tuned sharp in progressively larger increments. Higher octaves5, 6 and 7, on the other hand, are tuned flat from one another inprogressively smaller increments. Each note in an octave is detunedalmost an equal amount relative to other notes in the same octave, but adifferent amount relative to the notes of an adjacent octave. Thus, anapproximately equally tempered scale is maintained while the chorueffect is being created.

Although the illustrated tuning pattern is one which producesparticularly pleasant effects, other patterns may be obtained byadjusting the values for the resistors in bias network 24 and hence thechange in bias voltage appearing on octave bias busses 22-27. Forexample, emphasis of certain portions of the scale may be obtained byalternately detuning various octaves sharp or at with respect to aselected octave that is tuned to standard pitch, or a sharper sound maybe produced by reversal of the pattern shown in FIG. 2, such that higheroctaves are tuned progressively more sharp and lower octaves are tunedprogressively more flat. Reversal of tuning pattern such as that of FIG.2 may be achieved by tuning the organ to pitch with switch 40 in CHORUSposition, with the reverse tuning pattern being produced when switch 40is returned to the heretobefore NORMAL position. An example of a reversepattern is shown in FIG. 3, which is an exact reversal of the patternIof FIG. 2, while patterns illustrating alternating detuning are shownin FIGS. 4 and 5.

In addition, two positions of chorus control may be provided for asingle bank of tone generators, as, for example, a first pattern similarto that of FIG. 2 but with a lesser degree of detuning between adjacentoctaves and a second similar pattern providing the same degree ofdetuning as shown in FIG. 2. A switching arrangement by which twoposition chorus control may be carried out in an organ utilizing tonegenerators of the type illustrated in FIG. l is shown in FIG. 6. Biasnetwork 24 is in circuit in the same manner as in FIG. 1 to supply abias voltage to the bias busses of each octave as discussed. Choruscontrol switch 40 provided with additional fixed contacts for a secondchorus position, is shown in its normal position such that movableontacts 141 and 142 of each pole are connected to fixed contacts 143 and144 respectively. In this position contact 143 is connected to groundand contact 144 is connected to terminal 50 through resistor 152 toestablish the normal tuning bias for tone generators.

When switched to first chorus position (CHI) movable contact 141 isremoved from ground and engages fixed contact to receive a D.C.potential through from terminal 50 through resistors 154 and 154a inseries. Movable contact 142 is removed from fixed contact 144 andengages fixed contact 144a to receive a D.C. potential from terminal 50through resistor 152a, which potential is different from that providedwhen in its normal position. This causes a change in the bias voltagessupplied to the tone generators in the manner discussed in conjunctionwith FIG. 1, but to a lesser degree. When switched to the second chorusposition (CH2), movable contact 142 is opened while movable contact 141is connected to fixed contacts 145a and 145b to receive D.C. potentialderived from the junction between resistors 154 and 154a. Fixed contacts145a and 145b are arranged on the switch to be simultaneously connectedto movable contact 141. This causes the bias voltages supplied to thetone generators to be changed in the same manner as before. Theresulting detuning patterns are best illustrated in FIG. 2, where theoctave detuning provided with switch 40 in CH2 position provides thepattern of curve B as previously discussed. With switch 40 in theintermediate position (CH) a subdued detuning pattern shown by curve C(dotted) is provided. It can be seen from FIG. 2 that the organist hasthe option of selecting a pattern which will give either an accented ora subdued chorus effect.

A more versatile utilization of the foregoing chorus effect in organshaving more than one bank of tone generators is achieved by detuningeach bank of tone gen- 'erators independently of the others to the samegeneral pattern, but with each bank detuned to a different degree. Insuch an instance each bank of tone generators is provided with a biasingand switching arrangement as shown in FIG. 1. This enables the choruseffect to be produced between two or more pitches as described, andfurther when the same octaves are combined by playing the same manual aceleste effect is produced. This is best illustrated with reference toFIG. 7, wherein the pattern A shown in solid lines represents one bankof tone generators and the pattern B shown in dotted lines represents asecond bank of tone generators. Each pattern is similar to that of FIG.2, but with a different degree of detuning between adjacent octaves foreach bank of generators.

It can be seen that when played independently each bank of generatorswill produce the chorus effect as discussed, while the relative detuningbetween the same octaves of each bank can be combined to produce a onepitch celeste effect.

The foregoing method of producing a full chorus effect in an lorganhaving a limited number of independent tone sources may` also beaccomplished by producing fixed detuning of adjacent octaves accordingto a selected predetermined pattern. This is particularly advantageousin organs having tone sources Where a tuning shift is inconvenient orimpractical, such as those utilizing extremely stable oscillators astone sources or those utilizing so-called wheel generators as tonesources. Stable oscillators may, for example, be detuned a predeterminedamount with respect Ito standard pitch by adjusting the core of thetuned circuit inductor to develop selected pattern.

Standard wheel generator systems may be modified to provide octavedetuning by increasing or decreasing the whole frequencies imposed onthe tone wheels that have the notes of respective octaves thereon. Anindependent Wheel is provided -for each octave of the scale and rotatedat a different speed.. Thi-s will result in each octave being detunedaccording to a predetermined pattern with respect to an adjacent octave.For example, the A tone wheel (rotated at 60 c.p.s.) may be modified toprovide AZ at 111 c.p.s. (16 cents sharp with respect to the standard110 c.p.s.), A3 at 221 c.p.s. (8 cents sharp), A4 at 440 c.p.s. (intune), A at 878 c.p.s. (4 cents fiat), A6 at 1,754 c.p.s. (6 cents flat)and A7 at 3,506 c.p.s, (7 cents flat). When the tonewheels are rotatedat different speeds (for example 35.67540 for C, 44.94900 for E,67.34400 for B, etc.), there is produced similar detuning for eachoctave, with a resulting desired tuning pattern wherein the higheroctaves are vdetuned progressively sharp and the low octavesprogressively fiat.

The invention provides, therefore, an effective method and relativelysimple apparatus for creating a full chorus effect for an electric organhaving a limited number of tone sources. With a single bank of tonesources selected octaves or selected increments thereof are detuned afixed predetermined amount relative to adjacent octaves to provide mildbeats between octaves when notes or chords are played at two or morepitches. When used with organs having more than one bank of tonesources, it is further possible to provide a one-pitch celeste effect.Two or more tuning patterns may be provided to enable :the organist toutilize the chorus effect to greater or lesser degrees. It is possibleto detune progressively higher octaves sharp a decreasing amount and todetune progressively lower octaves flat an increasing amount forfullness of the musical effect. Other tuning patterns are also possibleto produce octave detuning which will emphasize different portions ofthe musical scale. When embodied in electronic organs a simple switchfor producing -the effect may be conveniently supplied with a stoptablet of the organ so that it can be used at the option of theorganist.

What is claimed is:

1. An electrical musical instrument including in cornbination, aplurality of tone generators for providing electrical tone signalsrepresenting the notes of a musical scale, each said tone generatorincluding circuit means having an electrical parameter responsive toapplied electrical signals for establishing the frequency of said tonesignals, means for applying an electrical signal .to selected groups ofsaid tone generators, each said group of tone generators providing anoctave of tones .for the musical scale, and circuit means for changingthe electrical signal applied to the tone generators of each octave by apredetermined amount, with the change in said electrical signal being'different for each octave relativeV to other octaves, whereby thetuning of each octave is shifted in relation to every other octave toprovide beats which create a chorus effect 2. An electrical musicalinstrument including in combination, a plurality of tone generators forproviding electrical tone signals representing the notes of a musicalscale, each said tone generator including circuit means having anelectrical parameter responsive to applied electrical signals forestablishing the frequency of said tone signals, means for applying anelectrical signal to selected groups of said tone generators, each saidgroup of tone generators providing an octave of tones for the musicalscale, and circuit means for changing the electrical `signal v appliedto the tone generators of each octave of the musical scale apredetermined amount, which predetermined amount -differs from thechange in the electrical signal applied to tone generators of otheroctaves in the musical scale by differing increments, with the higheroctaves of said musical scale being tuned fiat in progressively lsmallerincrements and the lower octaves being 4tuned sharp by progressivelylarger increments, thereby providing beats between the tones of eachoctave to create a chorus effect.

3. An electrical musical instrument including in combination, aplurality of tone generators for providing electrical signalsrepresenting the notes of a musical scale, each said tone generatorincluding oscillator means having a resonant circuit for establishingthe frequency of oscillations and meansfor sustaining oscillations insaid resonant circuit, each said oscillator means having a terminaladapted to receive a biasing potential to control the frequency ofoscillations established by said resonant circuit, circuit means forapplying a biasing potential to lsaid terminals for selected groups oftone generators, with each said group of tone generators providing anoctave of tones for the musical scale, and circuit means for changingthe biasing potential applied to each said group of tone generators apredetermined amount, which predetermined amount differs from the changeof biasing potential applied to other groups of tone generators, wherebythe notes of each octave of the musical scale are `detuned relative toother octaves an amount corresponding to the change in biasing potentialapplied to the tone generators therefor, thereby causing beats whichcreate a chorus effect.

4. An electrical musical instrument including in combination, aplurality of tone generators for providing electrical tone signalsrepresenting the notes of a musical scale, each said tone generatorincluding oscillator means having a resonant circuit for establishingthe frequency of oscillations and means for sustaining oscillations insaid resonant circuit, each said oscillator means having a terminaladapted to receive a biasing potential to control the frequency ofoscillations established by said resonant circuit, circuit means forapplying a biasing potential to said terminals for selected groups oftone generators, with each said group of tone generators providing anoctave of tones for the musical scale, and circuit means for changingthe biasing potential applied to each said group of tone generators apredetermined amount, which predetermined amount differs from the changein biasing potential applied to the tone generators of other octaves ofthe musical scale in differing increments, with said biasing potentialdecreasing in smaller increments for higher octaves and increasing inlarger increments for lower octaves of the musical scale, therebyproducing beats between the octaves to create a chorus effect.

y5. In an electric organ, the combination including a plurality ofindividual tone generators, each said tone v generator providing a toneof a frequency representing a trolling the frequency of oscillationsthereof, means providing-a plurality of biasing potentials of differentmagnitudes, circuit means for distributing each said biasing potentialto the terminal means of selected groupings of said tone generators,with each said grouping providing tone signals for an octave of themusical scale, and circuit means for changing each said biasingpotential a different predetermined amount relative to the change ofother biasing potentials, thereby detuning each said octave a fixedamount slightly different from the detuning of every other octave,whereby beats are produced between octaves to create a chorus effect.

6. In an electric organ, the combination including a plurality ofindividual tone generators, each said tone generator providing a tone ofa frequency representing a note in a musical scale, terminal means oneach said tone generator adapted to receive a biasing potential tocont-rol the frequency of oscillations thereof, means for providing aplurality of biasing potentials each of different magnitude, circuitmeans for distributing each said biasing potential to the terminal meansof selected groupings of said tone generators, with each said groupingproviding tone signals for an octave of the musical scale, and means forchanging each said bias-ing potential a predetermined amount differentrelative to the change of other biasing potentials, thereby detuningeach said octave such that some octaves are tuned sharp by differingamounts and other octaves are tuned flat by differing amounts, wherebybeats are produced between octaves to create a chorus effect.

7. In an electric organ, the' combination including a plurality ofindividual tone generators, each said tone generator providing a tone ofa frequency representing a note in a musical scale, terminal means oneach said tone generator adapted to receive a biasing potential forcontrolling the frequency of oscillations thereof, biasing network meansfor providing a plurality of biasing potentials each of a differentmagnitude, circuit means for distributing eac-h said biasing potentialto the terminal means of selected groupings of said tone generators,with each said grouping providing tone signals for an octave of themusical scale, and means connected to said biasing network means tocause the biasing potentials of the tone generators of selected higheroctaves to be decreased by progressively decreasing increments and tocause the biasing potential for the tone generators of selective loweroctaves to be increased by progressively increasing increments, with thetonegenerators of each octave being uniformly detuned an amountdiffering from the uniform detuning of the tone generators of everyother octave, thereby providing beats between the notes of each octaveto create a chorus effect.

8. In an electric organ, the combination including a plurality ofindividual tone generators, each said tone generator including anoscillator circuit to provide a tone of a frequency representing a notein a musical scale, terminal means connected with each said oscillatorto receive a biasing voltage for control of the frequency ofoscillations thereof, a voltage dividing network including a pluralityof series connected resistors, switch means operable between first andsecond positions, with said first position applying a direct currentpotential to selected points of said voltage dividing network to therebyprovide biasing voltages at the junction points between successive onesof said series connected resistors, circuit means connected betweenindividual ones of said junction points and the biasing terminals ofselected groupings of said oscillators, with each said grouping biasedto provide tone signals for an octave of the musical scale at apredetermined pitch, with a second position of said switch meansapplying said direct current potential to different selected points ofsaid voltage dividing network to thereby change the biasing voltagesprovided at said junction point, and with said biasing voltage changeproviding uniform detuning of each octave of tone generators bydifferent amounts relative to the detuning of the tone generators ofother octaves, whereby beats are produced between the notes of eachoctave t0 create a chorus effect.

9. In an electric organ, the combination including a plurality ofindividual tone generators, each said tone generator including anoscillator circuit to provide a tone of a frequency representing a notein a musical scale, terminal means connected with each oscillator toreceive a biasing voltage for control of the frequency of oscillationsthereof, a voltage dividing network including a plurality of seriesconnected resistors, switch means operable between first, second, andthird positions, with said first position applying a direct currentpotential to selected points of said voltage dividing network to therebyprovide biasing voltages at the junction points between successive onesof said series connected resistors, circuit means connected betweenindividual ones of said junction points and the biasing terminals ofselected groupings of said oscillators, with each said grouping biasedto provide tone signals for an octave of the musical scale at apredetermined pitch, with said second switch position changing saidbiasing voltages a first predetermined amount vand said thirdswitchposition changing said biasing voltages a second predeterminedamount, with said changes of said biasing voltages providing octavedetuning of said tone generators, whereby beats are produced betweennotes of each octave to create a chorus effect.

10. In an electric o-rgan, the combination including a plurality ofindependent tone generators, each said tone generator including anoscillator circuit to provide a tone of a frequency representing a notein a musical scale, terminal means connected to each said oscillator toreceive a biasing voltage for control of the frequency of oscillationsthereof, .a voltage dividing network including first and second parallelpaths, each path comprising a plurality of series connected resistors,circuit means including a first resistor for connecting one end of eachparallel path to la direct current potential supply, a plurality ofbiasing busses connecting the junction points of successive ones of saidseries connected resistors in each parallel path to the biasingterminals of selected groupings of said oscillator circuits, with theoscillator circuits of each said grouping providing tone signals for anoctave of the musical scale, a switch having first and second sectionsand operable between first and second positions, with said first switchsection having first and vsecond terminals and said second switchsection having first, second and third terminals, rneans connecting thefirst terminal of said first switch section to a junction betweenselected series resistors of said first parallel path, means including asecond resistor connecting the second terminal of said first switchsection to said direct current potential supply, means connecting theother end of said first parallel path to ground reference potential,means connecting the other end of said second parallel path to the firstterminal of said second switch section, means connecting the secondterminal of said second switch section to ground reference potential,and means connecting the third terminal of said second switch section tosaid direct current potential supply through said first resistor, sothat said switch when in a first position causes `biasing voltages tobedistributed to the tone generators of each octave to thereby tune eachnote to a predetermined pitch, and when in a second position changessaid biasing voltages for each octave of tone generators by differingamounts, thereby detuning each octave from said predetermined pitch adifferent amount relative to every other octave.

11. A musical instrument including in combination, a plurality of tonegenerators for providing tone signals representing the notes of amusical scale, each of said tone generators including first means forindependently establishing the frequency of said tone signals so thatsaid tone generators produce notes of the musical scale extending overseveral octaves, means for simultaneously operating generators for laplurality of octaves to produce a combination of tones, each ofsaidgenerators including second means for changing the tuning thereof,and control means including .a separate portion associated with saidgenerators of e-ach octave, said control means being opera-tive tochange the tuning of all of said tone generators for at least one ofsaid octaves by a predetermined fixed amount, so that the tones producedby the generators for said one octave 'are detuned with respect to thetones produced by the generators of another octave to produce beatsbetween octaves which create a chorus effect.

12. In an electrical musical instrument, the combination including aplurality of tone generators for providing tone signals representing thenotes of a musical scale which extend over a plurality of octaves, eachof said tone generators having means to establish the frequency `thereofincluding first and second portions, said rst portion being manuallyadjustable to establish the frequency of each tone generatorindependently of the frequency of the other generators, and controlmeans coupled to said second portion of each tone generator forsimultaneously detuning said tone generators of certain octaves by apredetenmined amount with respect to a standard pitch, whichpredetermined amount is substantially the same for the tone generatorsof each octave and differs for the tone generators of adjacent octavesaccording to a ypredeterf mined pattern, whereby beats are producedbetween the notes and chords of adjacent octaves to thereby create achorus effect.

13. In an organ having a keyboard, the combination including a pluralityof tone sources for providing tone signals representing the notes of .amusical scale which extend over a range of octaves, means actuated bythe keyboard for operating said tone Isources to simultaneously producetone -signals in different octaves, each of said tone sources havingfrequency determining means with first and second portions, said firstportion of each frequency determining means being adjustable toestablish the frequency of each tone source independently of thefrequency of other tone sources, and control means con-` nected to saidsecond portion of said frequency determining means of each of said `tonesources to control the frequency of said tone sources, said controlmeans including means to detune said tone sources of certain octaves,with the detuning being the same for all said tone sources of any oneoctave, and being related to the detuning of said tone sources ofadjacent octaves according to a predetenmined pattern, whereby beats areproduced between the notes of different octaves to create a choruseffect.

14. In an organ having a keyboard, the combination including a pluralityof tone sources for providing tone signals representing the notes of amusical scale which extend over a range of octaves, means actuated bythe keyboard for operating said tone sources to simultaneously producetone signals in different octaves, each of said tone sources havingfrequency determining means with rst `and second portions, said rstportion of each frequency determining means being adjustable toestablish the frequency of each tone source independently of thefrequency of other tone sources, and control means connected to saidsecond portion of said frequency determining means of each of said tonesources to control the frequency of said tone sofurces, said controlmeans including means to detune said tone sources of certain octaves,with the detuning being the same for all said tone sources of 'any oneoctave, and being such that higher octaves are detuned sharp and loweroctaves are detuned flat, whereby beats are produced between the notesof diiferent octaves to create a chorus effect.

References Cited by the Examiner UNITED STATES PATENTS 2,500,820 3/1950Hanert 84-1.24 X

ARTHUR GAUSS, Primary Examiner. D. D. FORRER, Assistant Examiner.

6. IN AN ELECTRIC ORGAN, THE COMBINATION INCLUDING A PLURALITY OFINDIVIDUAL TONE GENERATORS, EACH SAID TONE GENERATOR PROVIDING A TONE OFA FREQUENCY REPRESENTING A NOTE IN A MUSICAL SCALE, TERMINAL MEANS ONEACH SAID TONE GENERATOR ADAPTED TO RECEIVE A BIASING POTENTIAL TOCONTROL THE FREQUENCY OF OSCILLATORS THEREOF, MEANS FOR PROVIDING APLURALITY OF BIASING POTENTIALS EACH OF DIFFERENT MAGNITUDE, CIRCUITMEANS FOR DISTRIBUTING EACH SAID BIASING POTENTIAL TO THE TERMINAL MEANSOF SELECTED GROUPINGS OF SAID TONE GENERATORS, WITH EACH SAID GROUPINGPROVIDING TONE SIGNALS FOR AN OCTAVE OF THE MUSICAL SCALE AND MEANS FORCHANGING EACH SAID BIASING POTENTIAL A PREDETERMINED AMOUNT DIFFERENTRELATIVE TO THE CHANGE OF OTHER BIASING POTENTIALS, THEREBY DETUNINGEACH SAID OCTAVE SUCH THAT SOME OCTAVES ARE TUNED SHARP BY DIFFERINGAMOUNTS AND OTHER OCTAVES ARE TUNED FLAT BY DIFFERING AMOUNTS, WHEREBYBEATS ARE PRODUCED BETWEEN OCTAVES TO CREATE A CHORUS EFFECT.